Cool City Design: Integrating Real-Time Urban Canyon Assessment into the Design Process for Chinese and Australian Cities

Abstract

Many cities are undergoing rapid urbanisation and intensification with the unintended consequence of creating dense urban fabric with deep 'urban canyons'. Urban densification can trap longwave radiation impacting on local atmospheric conditions, contributing to the phenomena known as the Urban Heat Island (UHI). As global temperatures are predicted to increase, there is a critical need to better understand urban form and heat retention in cities and integrate analysis tools into the design decision making process to design cooler cities. This paper describes the application and validation of a novel three-dimensional urban canyon modelling approach calculating Sky View Factor (SVF), one important indicator used in the prediction of UHI. Our modified daylighting system based approach within a design modelling environment allows iterative design decision making informed by SVF on an urban design scale. This approach is tested on urban fabric samples from cities in both Australia and China. The new approach extends the applicability in the design process of existing methods by providing 'real-time' SVF feedback for complex three-dimensional urban scenarios. The modelling approach enables city designers to mix intuitive compositional design modelling with dynamic canyon feedback. The approach allows a greater understanding of existing and proposed urban forms and identifying potential canyon problem areas, improved decision making and design advocacy, and can potentially have an impact on cities' temperature.

Urban walkability profiles in Brisbane

“…The majority of studies developed on walkable communities have been developed in the temperate northern hemisphere. In contrast, areas in the southern hemisphere have their own challenges that require a better understanding of specific contexts (White et al, 2016).…”

Sky View Factors from Synthetic Fisheye Photos for Thermal Comfort Routing—A Case Study in Phoenix, Arizona

“…The SkyHelios model (Matzarakis & Matuschek, 2011) simulates continuous SVFs for small urban areas, but requires a geometric obstacle file. More recently, studies have presented continuous SVF calculations using 3D city models (Chen et al, 2012;Gál et al, 2009;Unger, 2009;White, Hu, Langenheim, Ding, & Burry, 2016), but these calculations usually do not incorporate vegetation. Tree canopy cover significantly reduces SVF at the pedestrian level and is an important shade source that should be incorporated in view factor analyses and outdoor thermal comfort assessments.…”

Cool Urbanism: The Radiant Exitance City

“…2 The proportion of visible sky above an observation point in an urban canyon is commonly measured as the sky view factor (SVF), a two-dimensional measurement between zero and one. SVF provides an indication of the extent to which urban form allows outgoing longwave radiation (radiant exitance) to be emitted freely to the sky, 3 and is therefore a critical consideration for city designs responding to heat.…”